1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (c) 2021 Western Digital Corporation or its affiliates.
4 * Copyright (c) 2022 Ventana Micro Systems Inc.
5 */
6
7 #include <linux/ftrace.h>
8 #include <asm/csr.h>
9 #include <asm/suspend.h>
10
suspend_save_csrs(struct suspend_context * context)11 void suspend_save_csrs(struct suspend_context *context)
12 {
13 context->scratch = csr_read(CSR_SCRATCH);
14 context->tvec = csr_read(CSR_TVEC);
15 context->ie = csr_read(CSR_IE);
16
17 /*
18 * No need to save/restore IP CSR (i.e. MIP or SIP) because:
19 *
20 * 1. For no-MMU (M-mode) kernel, the bits in MIP are set by
21 * external devices (such as interrupt controller, timer, etc).
22 * 2. For MMU (S-mode) kernel, the bits in SIP are set by
23 * M-mode firmware and external devices (such as interrupt
24 * controller, etc).
25 */
26
27 #ifdef CONFIG_MMU
28 context->satp = csr_read(CSR_SATP);
29 #endif
30 }
31
suspend_restore_csrs(struct suspend_context * context)32 void suspend_restore_csrs(struct suspend_context *context)
33 {
34 csr_write(CSR_SCRATCH, context->scratch);
35 csr_write(CSR_TVEC, context->tvec);
36 csr_write(CSR_IE, context->ie);
37
38 #ifdef CONFIG_MMU
39 csr_write(CSR_SATP, context->satp);
40 #endif
41 }
42
cpu_suspend(unsigned long arg,int (* finish)(unsigned long arg,unsigned long entry,unsigned long context))43 int cpu_suspend(unsigned long arg,
44 int (*finish)(unsigned long arg,
45 unsigned long entry,
46 unsigned long context))
47 {
48 int rc = 0;
49 struct suspend_context context = { 0 };
50
51 /* Finisher should be non-NULL */
52 if (!finish)
53 return -EINVAL;
54
55 /* Save additional CSRs*/
56 suspend_save_csrs(&context);
57
58 /*
59 * Function graph tracer state gets incosistent when the kernel
60 * calls functions that never return (aka finishers) hence disable
61 * graph tracing during their execution.
62 */
63 pause_graph_tracing();
64
65 /* Save context on stack */
66 if (__cpu_suspend_enter(&context)) {
67 /* Call the finisher */
68 rc = finish(arg, __pa_symbol(__cpu_resume_enter),
69 (ulong)&context);
70
71 /*
72 * Should never reach here, unless the suspend finisher
73 * fails. Successful cpu_suspend() should return from
74 * __cpu_resume_entry()
75 */
76 if (!rc)
77 rc = -EOPNOTSUPP;
78 }
79
80 /* Enable function graph tracer */
81 unpause_graph_tracing();
82
83 /* Restore additional CSRs */
84 suspend_restore_csrs(&context);
85
86 return rc;
87 }
88
